TITLE: GCN CIRCULAR NUMBER: 35766 SUBJECT: Swift GRB240221.92: Global MASTER-Net observations report DATE: 24/02/21 22:56:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich (Blagoveschensk Educational State University) MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB240221.92 (trigger No 1216743,16h 21m 22.32s , -15d 40m 33.6s, R=0.00130556) errorbox 2112 sec after notice time and 2135 sec after trigger time at 2024-02-21 22:44:39 UT, with upper limit up to 17.9 mag. Observations started at twilight. The observations began at zenith distance = 67 deg. The sun altitude is -13.8 deg. The galactic latitude b = 23 deg., longitude l = 360 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2383502 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 2146 | MASTER-Tunka | C | 20 | 17.4 | 2166 | MASTER-Tunka | C | 60 | 17.9 | Coadd 2176 | MASTER-Tunka | C | 20 | 17.2 | 2208 | MASTER-Tunka | C | 20 | 17.2 | 2239 | MASTER-Tunka | C | 20 | 17.4 | 2268 | MASTER-Tunka | C | 15 | 17.2 | 2292 | MASTER-Tunka | C | 15 | 16.9 | 2319 | MASTER-Tunka | C | 15 | 17.2 | 2343 | MASTER-Tunka | C | 15 | 17.1 | 2461 | MASTER-Tunka | C | 15 | 17.2 | 2485 | MASTER-Tunka | C | 15 | 17.0 | 2596 | MASTER-Tunka | C | 15 | 17.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/35766. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...